The process represented in the following scheme is known for producing a trans-5-aminopiperidine-2-carboxylic acid derivative, which is useful for an intermediate for pharmaceuticals.

In this method, L-pyroglutamic acid is protected by introducing a benzyl group at the carboxylic acid and introducing a tert-butoxycarbonyl group (a Boc group) at the amino group, and then coupling reaction with a sulfoxonium ylide is carried out. Next, the obtained compound is converted into a chloroketone, and is subsequently reacted with benzyloxyamine to obtain a corresponding imine derivative. Following deprotection of the above Boc group and the cyclization under basic condition lead to (S)-5-(benzyloxyimino)-piperidine-2-carboxylic acid benzyl ester. The reaction with borane-pyridine-complex in the presence of a hydrogen chloride leads to (2S)-5-(benzyloxyamino)-piperidine-2-carboxylic acid benzyl ester, then a salt is formed between oxalic acid, and the isolation is performed (Patent Document 1).